Every other day this question is asked...

All '73-'77.5 F250 4x4's are "highboys".

I don't know why they'd be harder to work on or to find parts for, as they are the same as all the other trucks made by Ford those years, beside suspension and axles. The motors are all the same, the bodies are the same, electrical, everything really... These trucks have lots of aftermarket support and parts suppliers.